This project will improve our understanding of the clinical use of dopamine and dobutamine in the pediatric age patient. The specific aims of the project are to 1) define the pharmacokinetics of dopamine in pediatric patients, 2) define the pharmacokinetics of dobutamine in pediatric patients, 3) to simultaneously study dopamine and dobutamine to determine if any pharmacokinetic interaction exist between these two drugs. In addition, information on the response of pediatric patients in terms of heart rate, blood pressure, and urine output will be measured and correlated with plasma concentrations of dopamine and dobutamine. Patients that are to receive dopamine and/or dobutamine on a clinical basis will have 1 cc blood samples obtained prior to, and at 30 and 60 minutes following initiation of drug infusion. Concurrent measurements will be made of heart rate and arterial blood pressure, and where available pulmonary artery pressures, arterial blood gases, pulmonary capillary wedge pressures and central venous pressure. Age, diagnosis, other drugs used in therapy, and indicators of renal and hepatic function will be recorded. Following any change in the rate of administration of dopamine and/or dobutamine, a repeat series of blood samples at 30 and 60 minutes will be obtained. Preliminary data will ascertain the effectiveness of 60 minute concentrations as being steady state concentrations. Samples will be analyzed for dopamine using high pressure liquid chromatography with electrochemical detection. Samples for dobutamine will be analyzed using high pressure liquid chromatography with fluorescence detection. The data will be analyzed for correlations between dose administered and concentration achieved as well as for the effect of other variables on the concentration-response relationship. These analyses will be performed on the DEC System 20 Computer for regression and analysis of variance. This study will provide a basic understanding of the relationship of dose of dopamine and dobutamine administered, concentration achieved in plasma, and pharmacologic response in the pediatric patient.